1. Field of the Invention
The present invention relates in general to automobile interiors, and more particularly, to a substrate for automobile interiors made of thermoplastic felt structure, which is lightweight, high-rigid, and impact-resistant.
2. Description of the Related Art
An automobile interior includes a main panel for a door trim, a rear shelf, a head liner, an instrument panel, a pillar, etc., and component such as an air bag, a switch, a speaker, a lamp, air conditioning components, decoration components, etc. combined to the main panel. The main panel is comprised of a substrate and a skin layer attached to the substrate, and fixed to the inside of the automobile by means of a retainer, a screw, etc.
The substrate must have sufficient stiffness and rigidity so as to keep a shape and to combine various components thereto, must not have sharp edges even if it is broken, and must have high impact-resistance.
In addition, it is desirable that the substrate is lightweight for enhancing the fuel efficiency, does not emit an odor, is recyclable, and has the low cost of materials and a simple manufacturing process in order to increase the productivity thereof.
As one example of a conventional automobile interior substrate, there is proposed a substrate which is molded by heat-pressing a resinated felt and a wood fiber. A main panel is formed by applying adhesives to the substrate, drying the substrate for a predetermined period of time, and adhering a skin layer to the substrate by vacuum forming. To the resinated felt and the wood fiber is needed to be added a hardening agent, namely, hexamine in order to promote a thermosetting property of a phenolic resin. The hexamine produces outgrowths like amine and ammonia at decomposition reaction. These outgrowths cause an offensive odor, and are noxious to a human body. Furthermore, the powdered phenolic resin produces fallout at a handling process thereof. Further, an offensive odor is given-off according as an organic solvent is volatilized in the process of applying the solvent type adhesives for adhering the skin layer to the substrate, thereby making working surroundings poor.
As another examples of conventional automobile interior substrates, there are proposed Korean patent application Nos. 98-013416, titled xe2x80x9cMethod of making automobile interiorsxe2x80x9d, and 98-013417, titled xe2x80x9cAutomobile interiorsxe2x80x9d. The automobile interiors have, as shown in FIG. 1, a substrate made of three layers. An intermediate layer 3 thereof is of a mat shape, and made by mixing a PP (Polypropylene) fiber with a flax fiber in the ratio of 5 to 5, and the other layers 1 are a sheet which is made by mixing a PP fiber with a polyester fiber in the ratio of 7 to 3. However, the above conventional automobile interior substrate has the following shortcomings.
First, in the process of manufacturing the mat 3, if weight per area of the mat is 1400 g/m2 or more, conveyor""s speed should be reduced according as a web is thicker in a web forming process. Then a needle-punching stroke should be prolonged and power for driving a needle-punching machine should be increased, so that the whole manufacturing processing becomes unbalanced and the equipments are overloaded. Further, a needle is likely to be broken, and the broken needle is likely to be embedded in the mat. Besides, the production speed is dropped.
Second, because the needle punching is performed in one direction, the mat has an asymmetric internal stress in a vertical direction. Thus, when the mat is preheated for making the automobile interior, the mat is deformed toward needle-punched surface, thereby causing such problems that the quality thereof deteriorates, the stiffness thereof is lowered in comparison with other automobile interiors having the same weight, and a heat-resistant property becomes inferior.
Third, because relatively various components such as PP fiber, flax fiber, and polyester fiber are employed in the automobile interior substrate, the recycling efficiency is also lowered.
Accordingly, the present invention has been made keeping in mind the above-described shortcomings and user""s need, and an object of the present invention is to provide a thermoplastic felt structure for an automobile interior substrate, which can prevent deformation thereof, with high rigidity and high impact-resistance.
Another object of the present invention is to provide a thermoplastic felt structure for an automobile interior substrate, which can enhance the fuel efficiency thereof with light weight and decrease the cost of material.
Still another object of the present invention is to provide a thermoplastic felt structure for an automobile interior substrate, which can decrease the cost of production with a simple manufacturing process.
This and other objects of the present invention may be accomplished by the provision of a thermoplastic felt structure for an automobile interior substrate, comprising a pair of mat units, each mat unit having a felt layer which is made by a mixture of a jute fiber and a PP fiber mixed in the weight ratio of about 5 to 5xcx9c6 to 4 and a PP foaming fiber adhered to one side of the felt layer, said mat units being coupled each other on the other sides of the felt layers.
Preferably, the jute fiber has about 40xcx9c120 xcexcm diameter and about 45xcx9c80 mm length. Herein, the jute fiber shows its excellence in stiffness and durability in comparison with another hemp fibers. That""s the reason why a jute fiber is employed.
Preferably, the PP fiber has about 6xcx9c15 denier diameter and about 45xcx9c80 mm length. At this time, if the diameter thereof is below the 6 demier, the cutting step is not easy, and if the diameter thereof is beyond the 15 denier, a uniform mixing is difficult.
Preferably, the PP fiber is comprised of a staple fiber having a crimp in order to improve the needle-punching efficiency.
Effectively, a weight per area of the PP foaming resin is about 50xcx9c100 g/m2.